“I wanna clear up something once and for all,” says Spike Lee in a new commentary track on the 20th anniversary DVD of “Do the Right Thing,” which was released on June 30, 1989. “Mookie did not throw the garbage can through the window to divert the mob from jumping on Sal” (Danny Aiello, the local pizzeria owner). Mookie, the delivery guy who works for Sal and is played by Lee, “threw the garbage can through the window because he just saw one of his best friends get murdered in cold blood by NYPD.” But Mookie’s friend wasn’t murdered and he wasn’t killed in cold blood. “Do the Right Thing,” the movie Barack and Michelle Obama saw on their first date, is still wrong after all these years – morally, politically, even at the basic level of language.

During a heated argument about whether the pizzeria’s wall of photos of Italian-Americans should include blacks because the shop is in the black neighborhood of Bedford-Stuyvesant, Brooklyn, Radio Raheem (Bill Nunn) blasts his giant boom box in Sal’s face.

Sal angrily tells Raheem to turn the music off, Raheem refuses, and in a shouting match Sal (who has spent the movie defending blacks against his racist son) uses the n-word against Raheem, smashing his radio with a baseball bat. Raheem, enraged, drags Sal over the counter, tackles him and starts beating him. Lee notes on another commentary track included with the new DVD, “If they don’t stop Radio Raheem he’s going to choke Sal to death.” The police arrive to pull Radio Raheem off Sal amid street pandemonium. As Raheem continues to resist three cops in a Rodney King-like tableau, one out-of-control officer ignores the cries of the crowd and a colleague and uses a choke hold (which was later banned in the NYPD) until Raheem dies.

This homicide isn’t murder because it isn’t premeditated. It may not be intentional, either, and it’s the opposite of “cold-blooded.” The police are aggravated and enraged and they lose their minds in the chaos. They’re hot-blooded.

The man who acts in cold blood is Mookie. He calmly assesses the situation and without any sign of a hot temper throws the garbage can through Sal’s window, sparking a riot. The police return and turn fire hoses on the rioters.

Lee says he wanted the audience to think about Bull Connor and Birmingham – a specious comparison that’s an insult to the peaceful victims of that racist attack.

To Lee the riot is something of a triumph – the bookend to the opening song “Fight the Power” – but the rioters have succeeded merely in driving the last white business out of their neighborhood, scaring away other potential job creators and raising everyone’s insurance premiums. The rioters also buy themselves several arrests – all in exchange for the satisfaction of attacking Sal for being white.

Unshown in the film – in which Bed-Stuy’s streets are so clean they appear to have been vacuumed and buildings sparkle because they were repaired and painted by the crew before filming – is the vicious circle in which places like Bed-Stuy, which are unattractive to business because of crime and drugs, repel jobs and leave more residents turning to crime and drugs. (No drugs appear in the movie, and the only weapon in the neighborhood is Sal’s bat).

Lee says on a commentary track that “The white audience, they are more concerned about the destruction of property, the destruction of Sal’s Famous Pizzeria, than they were about the death of Radio Raheem.” That’s about an inch from accusing most white viewers of this film of racism. It would be contemptible to value a white business more than a black life. Yet both Raheem’s and the cops’ acts of violence, detestable though they are, are in some sense understandable (not justified) because of emotions running hot.

Mookie’s act is utterly gratuitous. And if human life is, as Lee notes, more valuable than any property, he’s blind to the fact that it’s a black character, Raheem, who is the first in the film to cross this line, to repay property damage with bodily harm.

Lee, after all these years, is still stuck on rioters’ logic: If A harms B, than C should harm D. The neighborhood has a legitimate grievance with the police force, not with Sal, who isn’t a racist and whose most annoying act, to Mookie, is flirting with his sister.

Group guilt has been used against blacks so long (“I was mugged by a black guy, therefore I hate all blacks”) that you’d think Lee would recognize how poisonous the idea is. Instead he embraces it.

Like Barack Obama, born four years later, Lee came from the professional middle class (Lee’s father was a musician). Unlike Obama, Lee, who grew up in Cobble Hill, paints himself as cynical and streetwise.

The Obamas may have attended “Do the Right Thing” on their first date but in their rise they utterly rejected its message (if they were paying attention at all: Barack touched Michelle’s knee for the first time during the film). It sides with Louis Farrakhan and Al Sharpton (“Tawana told the truth,” says a graffito seen on a wall in the movie) in the cause of perpetual racial grievance – Us vs. Them.

Obama went to Harvard Law School, joining the power instead of fighting it, but Lee attended an all-black college – which he blasted for acting too white.

Obama built his presidential campaign around the idea that there is no Them, that we’re all Us. Lee today finds his ’80s anger out of touch, his audience having evaporated. “Do the Right Thing” and “Malcolm X” would turn out to be the highlights of his career; his latest racism movie, the turgid WWII drama “Miracle at St. Anna,” grossed $8 million and was instantly forgotten.

Lee, who famously ended “Do the Right Thing” with two quotations – one from Dr. King urging nonviolence, the second, more belligerent one from Malcolm X – has suggested that there must be some middle ground. Where’s the compromise between violence and peaceful protest? Throwing styrofoam rocks? Bitter shouting matches?

Barack Obama turned his back on such nonsense. If he had ever shown a touch of Farrakhan about him, he would not be president today, and it was his unflappable cool during the financial crisis that clinched his victory. Spike Lee, who ended the credits of “Do the Right Thing” with the words “by any means necessary,” was wrong. Blacks can reach the summit – without anger, without animosity, without fighting the power.